Ganges River Dolphin

(Platanista gangetica gangetica)

INFORMATION AND CHARACTERISTICS.

It is one of two subspecies of the South Asian river dolphin (Platanista gangetica), and it has the title of the national aquatic animal of India, where is also called Ganges susu or shushuk.

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

The Ganges River dolphin and its closely related subspecies, the Indus River dolphin, have an appearance quite different from that of oceanic dolphins. Specifically, this species has the following characteristics:

Morphology.
It has a robust body with an asymmetrical skull, a protruded front, and a very flexible neck. Its long snout measures almost 20 percent of its body length and in adult females is even longer than that of the males. It has a small crest on the melon.

The dorsal fin is a little triangle with a broad base, and the longer pectoral flippers are flat. Its eyes are tiny.

Order: Cetacea
Family: Platanistidae
Genus: Platanista
Species: Platanista gangetica

Weight and size.
An adult has a length between 2 and 2.2 meters, and it has an approximate weight of 51-89 kilograms.

Skin Coloration.
The body has a dark gray or brown color, with a lighter color in the ventral area.

Distinctive characteristics.
It’s hard to differentiate a Ganges River dolphin from an Indus River dolphin, but the former species has a slightly longer tail than that of its relative.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

The Ganges River dolphin distribution is limited to the east of India. It inhabits the freshwater system Ganges-Brahmaputra-Megna (GBM) and the Karnaphuli-Sango river systems, and their tributaries, which run through Nepal, Bhutan, and Bangladesh.

It Inhabits large sections of these rivers or their tributaries from the tidal zone to the foothills of the Himalayas, the Cachar Hills (District of India) and the Garo Hills of Meghalaya (Indian state). During the flooding season, this dolphin leaves the main canals and reach the temporary tributaries and flooded lowlands.

It is most frequently found in bodies of countercurrent water located between the convergence of channels and meanders (pronounced curves) and occasionally go to channels and reservoirs. Their habitat has a depth of 3 to 9 meters, and water temperatures between 8 and 33 Celsius degrees.

WHAT DO THEY EAT? DIET AND EATING HABITS.

The Ganges River dolphin has a carnivorous diet which includes a large variety of fish and invertebrate animals; perhaps it is also capable of consuming birds and turtles. These are some of their usual prey:

– Common carp.
– Gobio.
– Prawn.
– Freshwater sharks.
– Mahseer fish (Family Cyprinidae).
– Shrimp.

Although it has visible teeth in the jaws, it does not use them to chew but to hold their prey firmly. Its eyes are not useful to find food because in the muddy waters of its habitat they are not required, that is, it is an animal functionally blind, so it uses echolocation to detect prey.

This dolphin usually swims with a fin touching the riverbed to feel the sediments since animals hide there. Its snout is very useful for this. Once it finds a suitable prey, it holds the victim with the jaws and begins to swallow it whole starting from the head so that the scales (if the prey has them) do not hurt its throat.

It does not always look for food at the riverbed. Its most common practice is finding a school of fish near the surface and drag them to the bottom to eat them.

HOW DO THEY BEHAVE? BEHAVIOR.

The maximum speed that this dolphin reaches when swimming in its natural habitat is 27 kilometers per hour.

This dolphin has a shy, quiet and rather passive behavior. It swims alone or with 1 or 2 more individuals (pods may have 2-10 members) and rarely gather in large groups although some people report sightings of groups with up to 30 members. It is probably a semi-gregarious and territorial animal since sometimes it chases other dolphins aggressively. Their leaps out of the water are related to reactions to aggressions or external disturbances.

The primary function of the sense of echolocation in this species is searching for food rather than communicating. An unusual behavior observed in this species is the habit of swimming sideways, especially to the right. The reason is unknown. The maximum speed that reaches when swimming in its natural habitat is 27 kilometers per hour.

During the rainy season, this dolphin ventures into the tributaries of the river and returns to the main canals in the winter.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

The Ganges River dolphin mates throughout the year and not in any specific season. The first breeding occurs between six and ten years of age and females give birth once every 2 or 3 years. It is a relatively large interval that, together with the late maturation, produce a low natality rate that does not contribute to increasing the number of individuals in the wild.

It is not known the process of courtship and mating, and a calf is born 8 to 12 months after the intercourse more frequently between December and January and between March and May. Maternal care is presumed to be similar to that of other dolphin species, but in this case, after weaning (1 year after birth), the offspring do not maintain ties with its mother.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation status: “Endangered.”

As is frequently the case in the world of dolphins, the greatest threat to this species are humans who, looking for their meat and oil, have hunted them for many years putting them close to extinction.
According to the Red List Of the International Union for the Conservation of Nature (IUCN), this subspecies has a conservation status of endangered.

These dolphins do not have many predators in their habitat, so most of their threats are anthropogenic like:

– Dam construction.
These structures separate different populations of the same species which reduces the genetic diversity and the amount of mature individual available to mate.

– Bycatch.
They are sometimes trapped or entangled in fishing nets and other devices which are not intended to hunt these cetaceans.

– Pollution.
The contamination of the Ganges river comes from chemicals, garbage, residual waters and industry spills.

There are less than 2,000 Ganges dolphins left in the wild and a few time to help them survive in this challenging context. But the cause is not entirely lost, as the Indian Wildlife Protection Act looks for the protection of this species as a priority. Also, international organizations such as the WWF (World Wide Fund for Nature) have established programs to move from theory to practice and reduce the degradation of this dolphin’s habitat.

References

http://www.iucnredlist.org/details/41758/0

Rashmi Sanghi. Our National River Ganga: Lifeline of Millions. Springer Science & Business Media,  2013.

http://s3.amazonaws.com/academia.edu.documents/46348097/Sources_and_Accumulation_of_Butyltin_Com20160608-24155-1njpezf.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1489183099&Signature=0jehfoy3PH4ix9VZ15G6QKFQMVU%3D&response-content-disposition=inline%3B%20filename%3DSources_and_accumulation_of_butyltin_com.pdf

Mammals in the Seas: Small cetaceans, seals, sirenians and otters. Food & Agriculture Org., 1978.

http://animaldiversity.org/accounts/Platanista_gangetica/

(Inia Geoffrensis)

INFORMATION AND CHARACTERISTICS.

Other common names of this dolphin are Boto, bufeo and pink river dolphin. Among the river dolphins, this species is the largest, best known, most researched and with the largest population. There are three subspecies of Amazon river dolphin:
– Inia geoffrensis geoffrensis.*
– Inia geoffrensis humboldtiana.
– Inia geoffrensis boliviensis.

* Recently (2014) this subspecies was split from Inia geoffrensis and defined as an independent species with the name Araguaian River dolphin as mitochondrial studies determined that they are indeed different species.

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

Morphology.
It is a robust dolphin with a very long snout easily distinguishable. It has a bulbous forehead due to a pronounced melon, chubby cheeks, small eyes and a remarkably flexible neck since its vertebrae are not fused. The pectoral flippers are large and have a triangle shape. He has a heterodont denture since his teeth are conical in the front of the jaw while the back pieces have a flange.

Order: Cetacea
Superfamily: Inioidea
Family: Iniidae
Genus: Inia

Weight and size.
Adults are between 1.53 and 2.4 meters in length, but this depends on the subspecies in question. The largest individual recorded was a female, weighing 98.5 kilograms.

Skin Coloration.
The most distinctive feature of this dolphin is the pink color that it acquires with age. The lower part of the body is usually clearer, and some individuals have gray patches.

Distinctive characteristic.
It is the only species of cetacean with heterodont dentition, and its dorsal fin is so small that it rather looks like a triangular crest.

Amazon River Dolphin – Inia Geoffrensis.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

The Amazon River dolphin inhabits only the freshwater systems of South America. Its distribution includes the basins of the Amazon and Orinoco rivers and the tributaries of these rivers in Bolivia, Colombia, Brazil, Ecuador, Peru, and Venezuela. However, each subspecies lives in defined areas: I. g. Geoffrensis thrives in the Amazon and Araguaia river basins except for the upper Teotonio rapids in the Madeira river basin in Bolivia. I.g. Boliviensis inhabits above the Teotonio rapids in the basin of the Amazon River and, I. g. Humboldtiana dwells in the basin of the Orinoco River.

The Amazon River dolphin can live in areas of slow movement, in deep water channels, in flooded forests, in confluences where clear waters and sewage mix, in narrow channels and possibly under waterfalls and rapids.

WHAT DO THEY EAT? DIET AND EATING HABITS.

The Amazon pink dolphin consumes a variety of prey more diverse than other species of dolphins. Fish, crabs and small turtles are part of the diet of this cetacean that regularly hunts alone and consumes 2.5 percent of its total weight each day.

The diet of these dolphins includes 43 species of fish. Their favorite fish belong to the families Sciaenidae, Cichlidae, and the one of the feared piranhas, Serrasalmidae.

It is a natural hunter. Mostly active during the day, it knows that under the waterfalls or at the mouths of the rivers, it is easier to catch the fish that pass through the currents. Sometimes it looks for food at the riverbed. The hard shells of turtles do not deter this dolphin from eating these reptiles because for such prey it has a potent and long “snout” that helps break the hard parts.

Sometimes it associates with the giant otter (Pteronura brasiliensis) or the tucuxi (Sotalia fluviatilis) to hunt in a coordinated way and share the food.

HOW DO THEY BEHAVE? BEHAVIOR

Observations concluded that the Amazon River dolphin moves slowly. Its speed while swimming is only 1.5 to 3.2 kilometers per hour, but it has occasional bursts reaching up to 14 to 22 kilometers per hour.

It is not as sociable as the oceanic dolphins since it usually travels in groups of 2 or 3 individuals, mostly mothers with a calf. It is, therefore, a lone dolphin. The larger groups, with 12 to 15 members, are temporal associations with the purpose of feeding or mating.

It is somewhat shy with humans, but sometimes it shows curiosity. It is also very playful, and it has been seen pulling the aquatic grass and throwing pieces of wood. Curiously, at times its food is also its friend: it usually plays with fish and turtles.

It uses echolocation to perceive what is in its environment and capture prey. The “clicks” are the basis of their communication and reach from 16 to 170 kilohertz.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

Scientists believe that this species is monogamous, but after noticing the male’s aggressiveness during mating and the multiple scars on its body, they began considering the idea of polygamy because this is the evidence of a possible competition for females.

Males and females reach sexual maturity at about five years of age or when the former is already about 2 meters in length, and the latter is between 1.60 and 1.75 meters. When a male finds a receptive female, he communicates his mating intentions by biting the female’s flippers.

11 months after mating, a single offspring is born between May and July measuring about 0.8 meters long. The time between each birth can last up to 5 years.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation Status: Data Deficient.

The fact that the pink dolphin has a “Data Deficient” conservation status on the Red List of the International Union for the Conservation of Nature entails a danger not completely unknown, but that makes difficult to implement conservation strategies. It is evident that the species faces a serious problem for survival in its natural habitat and until 2011 had a classification as a vulnerable species.

Their principal anthropogenic threats are:

– Overfishing.
This practice reduces the availability of food for the species.

– Dam construction.
The development of hydroelectric dams in the river, alter the conditions of their habitat separating populations which reduce the availability of mating partners and the genetic diversity.

– Uncontrolled logging.
When logging for converting the forests into agricultural land, the number of animals consuming the products of the trees decreases, and the amount of food for the Boto reduces in consequence.

– River traffic.
Excessive boat traffic causes collisions with these dolphins where the propellers cause them serious injuries.

– Habitat pollution.
The increasing contamination of the river brings all kind of problems to these dolphins and reduces their chances to survival drastically.

In their natural habitat, alligators, jaguars, anacondas and Bull sharks (Carcharhinus leucas) are their major threats. In Brazil, Peru, Venezuela, Colombia and Bolivia, there are laws to protect this species. Since 1986, the Cetacean Specialist Group of the Species Survival Commission has been working to protect and design conservation strategies for all endangered river dolphins.

Amazon River Dolphin Infographic!

(Click for expand)

References

Annalisa Berta. Whales, Dolphins, and Porpoises: A Natural History and Species Guide. University of Chicago Press, 2015.

William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009. Page 26

Sy Montgomery. Journey of the Pink Dolphins: An Amazon Quest. Chelsea Green Publishing, 2009.

http://www.iucnredlist.org/details/10831/0

http://ufdc.ufl.edu/UFE0046251/00001

]]> https://www.dolphins-world.com/chinese-river-dolphin/ Tue, 25 Apr 2017 15:00:28 +0000 http://www.dolphins-world.com/?p=109 Author of the drawing: Alessio Marrucci.

Chinese River Dolphin or Baiji Dolphin

Lipotes vexillifer

INFORMATION AND CHARACTERISTICS.

The Chinese river dolphin or Baiji is the rarest freshwater cetacean of all. This affirmation has little to do with their physical appearance and their rare sightings, given the great danger that runs in their natural habitat. In fact, since 2006 nobody has seen a specimen alive, so presumably is already extinct.

Its name in Chinese, Baiji, means “white dolphin” and is known by the nickname of “the goddess of the Yangtsé,” regarding the river that inhabited.

Order: Cetacea
Superfamily: Lipotoidea
Family: Lipotidae
Genus: Lipotes

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

This river dolphin is small, with a body fully adapted to life in freshwater systems.

Weight and size.
There is sexual dimorphism since adult females are slightly longer than males. The male length is on average 2.3 meters, and the female is 2.5 meters. Their weight ranges between 135 and 320 kilograms.

Morphology.
It has a fusiform body like the other species of dolphins, but more robust. It has a small head with a prominent melon. The skull is devoid of maxillary ridges. The eyes are quite small in comparison to those of the oceanic dolphins, and this is because in the muddy water of its habitat they do not need to have good visibility. Their round pectoral flippers are very long, and the dorsal fin is short, triangular and situated in the posterior part of the dorsum.

Skin Coloration.
It exhibits countershading characterized by bluish-gray color in the dorsal region and white in the lower part of the body.

Distinctive characteristics.
When this dolphin swims just below the surface of the river, its small dorsal fin protrudes and resembles a flag, so the locals call it “white-flag dolphin.” Another way to recognize the Baiji dolphin is by observing its very long and narrow beak which has the tip curved upwards.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

This species is endemic to the Yangtze River in China but also lived in the Poyang and Dongting lakes of the same country some time ago. Its distribution range extends from the mouth of the Yangtze River to the Gezhouba dam. The last sightings occurred in the middle and lower parts of the Yangtze River.

It inhabits only fresh water and has a marked preference for the tributaries of the river and where there are swirling sandbanks.

WHAT DO THEY EAT? DIET AND EATING HABITS.

The Baiji is a carnivore that feeds on a variety of small fish. It uses its long “beak” to explore the muddy riverbed and detect hidden prey since its vision is not very good. However, it has a highly developed sense of echolocation.

It submerges for 10 or 20 seconds, catch its food and comes back to the surface. It probably does not has preferred prey, but prioritize the capture of large animals.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

Evidently, there is not enough information about this dolphin. The mating system of the Baiji is unknown, but there are two mating seasons per year; The first during the spring and the second during the summer. The highest reproduction time occurs during the first half of the year.

These dolphins reach sexual maturity between 4 and six years of age. After mating, the pregnant female has a gestation period of 10 to 11 months although other estimates indicate that it can be 6 and up to 12. Deliveries occur between February and April, and the offspring are born with a length of 1 meter.

The mother provides dedicated care to the newborn calf helping it to reach the surface to breathe, teaching it to catch food and keeping it close to her, even after weaning.

HOW DO THEY BEHAVE? BEHAVIOR

This cetacean is rather timid, and that is why it is so difficult to observe in its natural habitat. This fact gives hope about its possible extinction.

They usually live in small groups of 3 or 4 dolphins or pairs; The largest pod on record was 16 members. Occasionally they are associated with finless porpoises (Neophocaena phocaenoides), cetaceans of fresh water that also undergo a severe decrease of population.

The groups spend most of the day in water swirls looking for food, but they are more active during the nights and until the mornings. They usually rest in areas of slow currents. They communicate by whistles and clicks. They use the latter when they identify prey or other objects in their environment.

Their dives are shallow, boats have seen them on very few occasions. If they come to the surface to breathe, they do it with minimal splashing. Their breathing intervals are short: they last between 10 and 20 seconds; Maximum of 200 seconds.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation Status: Extinct.

The populations of Chinese river dolphins dramatically began to decrease since China became industrialized. Many cities prospered on the banks of the Yangtze River, and this situation affected the endemic species.

At the beginning of the 1980s, there were approximately 400 specimens. A few years later the number was reduced to 300. By the end of the decade of the 1990s there were 13 individuals, and by 2006, researchers did not find a single Baiji dolphin in the river, so it is possible that it is extinct in the wild. A sighting report in 2007 restored the hope, but unfortunately, the existence of a few individuals is not enough to save the species.

The main threats that Baijis faced and took them to the extinction were:

– Bycatch.
– Illegal fishing. Using electricity and rolling hooks.
– Overfishing. An activity that reduced the number and diversity of available food.
– Contamination produced by companies and factories near the river.
– Collisions with boats.
– Construction of dams that split populations.

This dolphin is protected in China since 1975 and in 1986 Chinese biologists established protection strategies. They even created a dolphin reserve along the Yangtze (Baiji Xin-Luo National Reserve), but obviously, it was too late to get results. Currently, the patrol boats of the reserve are responsible for supervising the compliance of the protection measures and investigating sightings and deaths of species that inhabit the river, but sadly these dolphins are not there anymore.

References

William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009. Page 71.

http://www.cms.int/reports/small_cetaceans/data/L_vexillifer/L_vexillifer.htm

http://animaldiversity.org/accounts/Lipotes_vexillifer/

http://www.fisheries.noaa.gov/pr/species/mammals/dolphins/chinese-river-dolphin.html

Did you know that dolphins swim up to five times faster than the best human Olympic swimmer? Many think that this is obvious, since they are aquatic animals; however, they are mammals like humans. This is the reason why they are doing experiments to measure their speed and energy usage. It should be noted that those studies do not threaten the lives of these beautiful aquatic mammals.

//www.youtube.com/watch?v=zp-Po76p5pw

Introduction

There are only five species of dolphins that are able to thrive in freshwater and the Amazon River Dolphin is one of them. Many people assume that all dolphins live in saltwater so this is interesting to learn if you weren’t aware of it. There are several subspecies of River Dolphins to learn about.

Description

Depending on the location where they reside, River Dolphins will vary in size. Some of them can be up to 8 feet long but most of them are much smaller than that. They can also be found in a variety of colors. Some that you are known to exist include gray, black, brown, pink, yellow, and white. Due to the many different colors, they are often mistaken for other forms of aquatic life.

Distribution

The River Dolphin, as the name implies, lives in Rivers and that means they are able to survive in freshwater. They tend to stick to the brackish and coastal regions. They are found in the

Amazon, Ganges, Yangtze, Mekong, and Indus Rivers. Many of these rivers are home to very poor villagers and the locations can be very dense.

Plenty of these rivers are filled with dark, murky water and plenty of pollution. What is very interesting is that they can live in conditions that other species of dolphins would not be able to. It isn’t understood why this is possible, and more research has to be done. With so few species being able to live in freshwater, there are some theories but no definite answers at this time.

Behavior

River Dolphins are very social, and like others, they form pods. There can be just a few of them or more than 100 in a pod. They do form very strong bonds and they are quite protective of each other. The young tend to be secured in the middle of the pod in order to keep them safe. The females have also been noted to care for the young of each other in a cooperative effort.

These dolphins are believed to be very social and to have a complex hierarchy that can be hard to fully understand. They tend to have some pods that have primarily females or males in them. This could be part of their social organization.

Feeding

Fish are the main components of the diet for the River Dolphin, and they can eat large amounts of them daily. They use a variety of differenttechniques to get the schools of fish with ease. Usually, these efforts involve teamwork and collaboration that is very in sync and interesting to observe. For larger pods, they often break up into smaller groups for feeding purposes to be carried out.

Reproduction

The time of year for mating can vary based on the location of the River Dolphin. The females usually are ready to mate around 8 years of age and for the males it is about 10 years old. The males may heavily compete with each other for mating. The young will be born from 10 to 12 months later, tail first.

The pod is very protective and they will help the mother during the birthing process. They will protect the young calf and help it to the surface for air. They will also help keep predators away. The young will grow rapidly due to the fat content found in the milk that the mother produces. They will drink the milk for 1 ½ to 2 years, but they will also start to consume fish when they are about 6 months old.

Conservation Status and Threats

The River Dolphin is considered to be in a range from vulnerable to critically endangered. It is hard to get a good idea of the number of them due to the different species and their habitat. There are plenty of issues for the River Dolphin to worry about in their natural habitat. They may be caught up in fishing nets or collide with boats. Heavily pollution has played a vital role in the reduction of numbers of them in many locations.

Some of the conservation efforts involve fishing with better equipment and tools. However, since the rivers where plenty of the dolphins live are around very poor cultures that can be tough to improve. Overfishing is also a concern as the villagers heavily depend on the food for survival. Yet that can leave a lack of food for the dolphins to survive. Pollution problems are also higher in areas where they don’t have proper water and sewer systems in place.

One of the River Dolphins called the Baiji, has declared functionally extinct in December of 2006. The last time one of them was seen in the wild was in 2004. While there were some reports in 2007 of sightings of one in the Yangtze River, it couldn’t be confirmed.

The pink river dolphin is a freshwater dolphin who lives in the Amazon and Orinoco rivers in South America. They are also known as Boto, and their scientific name is Inia geoffrensis. Although usually, they are pink, sometimes they are also gray, white or a mix of these colors. The pink dolphin of Hong Kong (Sousa chinensis) is another species with pink color mixed with gray, but they are entirely different species that live in far away from each other.

One of the theories that explain the reason for its unusual coloration is related to its social behavior. Some think that fights between some specimens, especially males, leave visible scars on their skin that turn pink with the passage of time.

Other researchers suggest that it is a natural way to camouflage themselves against predators, as reddish coloration is very common in the waters of their aquatic environment.

Pink river dolphins live in the main rivers of the Amazon River and the Orinoco river in South America.

They are endangered because of the increase in population in the basins of these two rivers, increasing the pollution, the river traffic and therefore the accidental killing.

Also, the construction of dams and the pluvial projects have damaged their habitat taking them inevitably to a slow extinction.

The Boto dolphin (Inia geoffrensis), inhabits the Amazon basin and part of the Orinoco river basin, so it has a wide variety of species available to eat, although it prefers fish since it feeds on more than 43 types, including the feared piranhas. Complementary this dolphin also eats crabs and turtles.

It consumes about 2.5% of its body weight daily.

The Amazon River dolphin, also known as Boto (Inia geoffrensis), is a freshwater dolphin that lives in the Amazon River and the Orinoco River systems which include several countries in South America.

These dolphins are Pink Dolphins move around these rivers to every place where they can reach without going to the ocean.

Other pink dolphins such as the Chinese white dolphin (Sousa chinensis) live in an area that covers the east and west coasts of northern Australia, eastern China, the Indo-Malayan archipelago, and the Bay of Bengal in the east of India.

Yangtze river dolphins, also known as Baiji are freshwater dolphins who lived in the Yangtze River in China.

Due to excessive fishing and industrialization around the Yangtze River, this species of dolphin is critically endangered, and even some affirm that it is already extinct.

Baiji used to live along 1000 miles of the middle and lower parts of the Yangtze River from the mouth of the river near Shangai to Yichang in the west.